Synergistic antitumor activity of capecitabine in combination with irinotecan

5-Fluorouracil (5-FU) and capecitabine alone and in combination with irinotecan/oxaliplatin are clinically active in the treatment of colorectal and other solid tumors. Studies of the antitumor activity and toxicity of capecitabine or irinotecan alone and in combination with each other, were compared with 5-FU and raltitrexed in human tumor xenografts of colorectal and squamous cell carcinoma of the head and neck using clinically relevant schedules. Antitumor activity and toxicity were evaluated in nude mice bearing human colon carcinomas of HCT-8 and HT-29 and in head and neck squamous cell carcinomas of A253 and FaDu xenografts using the maximum tolerable dose of single-agent capecitabine, 5-FU, or raltitrexed, or each of the drugs in combination with irinotecan. Mice were treated with capecitabine and irinotecan alone or in combination using 2 different schedules: (1) capecitabine orally once a day for 7 days and a single dose of irinotecan (50 mg/kg intravenously [I.V.]), with each drug alone or in combination, and (2) capecitabine orally 5 days a week for 3 weeks and irinotecan 50 mg/kg (I.V. injection) once a week for 3 weeks, with each drug alone or in combination. For comparative purposes, the antitumor activity of single-agent capecitabine, 5-FU, or raltitrexed, or each drug in combination with irinotecan was carried out at its maximum tolerated dose (MTD) using a 3-week schedule. Results indicated that HT-29 and A253 xenografts were de novo resistant (no cure) to capecitabine and irinotecan alone at the MTD, whereas HCT-8 and FaDu xenografts were relatively more sensitive, yielding 10%-20% cures. The combination of irinotecan/capecitabine was much more active than either drug alone against all 4 tumor models. The cure rates were increased from 0 to 20% in A253 and HT-29 xenografts and from 10%-20% to 80%-100% in HCT-8 and FaDu tumor xenografts, respectively. Irinotecan/capecitabine had clear advantage over irinotecan/5-FU and irinotecan/raltitrexed in efficacy and selectivity in that they were more active and less toxic. The extent of synergy with irinotecan/capecitabine appears to be tumor-dependent and independent of the status of p53 expression. The potential impact of the preclinical results on clinical practice for the use of these drugs in combination needs clinical validation.     

Antitumor activity of ZD1694 (tomudex) against human head and neck cancer in nude mouse models: role of dosing schedule and plasma thymidine.

We studied the antitumor activity and toxicity of ZD1694 (tomudex), a specific inhibitor of thymidylate synthase (TS), in nude mice bearing human head and neck squamous cell carcinoma A253 and FaDu xenografts. Mice were treated by single i.v. push (i.v. x 1), i.v. push once a week for 3 weeks (weekly x 3), and i.v. push once a day for 5 days (daily x 5), and the maximum tolerated doses (MTDs) of ZD1694 were 300 mg/kg, 60 mg/kg/week, and 30 mg/kg/day, respectively. ZD1694 was moderately active against both A253 and FaDu xenografts. Antitumor activity was schedule-dependent in both tumors: weekly x 3 > or = i.v. x 1 > daily x 5. In contrast, the rank order of toxicity was daily x 5 > weekly x 3 > or = i.v. x 1. ZD1694 at the MTD produced 20% complete tumor regression and 20% partial tumor regression (PR) with i.v. x 1 and weekly x 3 schedules and 12-day tumor growth delay with daily x 5 schedule against FaDu xenografts. No complete tumor regression was achieved with ZD1694 with any schedule against A253; a 20% PR, 40% PR, and 10-day tumor growth delay were observed with i.v. x 1, weekly x 3, and daily x 5 schedules, respectively. The data indicate that ZD1694 was slightly more effective against FaDu than against A253. Of interest and potential clinical importance was the observation that ZD1694 was still active at doses lower than the MTD (> or =1/3 MTD), which showed a high therapeutic index and wide safety margin. Study of ZD1694 compared with 5-fluorouracil and 5-fluoro-2'-deoxyuridine at the MTD revealed that the antitumor activity of ZD1694 was comparable with or superior to 5-fluorouracil and 5-fluoro-2'-deoxyuridine against both A253 and FaDu xenografts, with less toxicity. High plasma thymidine in mouse relative to human (approximately 1.3 microM and <0.1 microM, respectively) may complicate the study of antitumor activity and toxicity of TS inhibitors with human tumor xenografts grown in the mouse. To test this hypothesis, we preadministered methoxypolyethyleneglycol-conjugated thymidine phosphorylase (MPEG-TPase; 2500 units/kg/dose) to reduce mouse plasma thymidine, then treated with various doses of ZD1694 using the daily x 5 or i.v. x 1 schedules in the A253 tumor model. MPEG-TPase significantly increased the toxicity of ZD1694; the MTD of ZD1694 plus MPEG-TPase was reduced 3- and 10-fold compared with ZD1694 alone for i.v x 1 and daily x 5 schedules, respectively. However, preadministration of MPEG-TPase did not potentiate the antitumor activity of ZD1694 with either schedule. The data indicate that the study of TS inhibitors in rodent models may not be suitable for predicting a safe dose for clinical study. However, rodent models, particularly human tumor xenografts, are still useful models for evaluation of antitumor activity and schedule selection for TS inhibitors.     

Se-methylselenocysteine offers selective protection against toxicity and potentiates the antitumour activity of anticancer drugs in preclinical animal models

Background:

Identification and development of drugs that can effectively modulate the therapeutic efficacy and toxicity of chemotherapy remain an unmet challenge. We evaluated the effects of Se-methylselenocysteine (MSC) on the toxicity and antitumour activity of cyclophosphamide, cisplatin, oxaliplatin, and irinotecan in animal models.

Methods:

Cyclophosphamide, cisplatin, and oxaliplatin were administered by a single i.v. injection and irinotecan by i.v. weekly × 4 schedules. For the combination, MSC was administered daily via the oral route for 7 days in mice and daily for 14 days in rats before and concurrent with drug administration.

Results:

Se-methylselenocysteine significantly protected against organ-specific toxicity induced by lethal doses of cyclophosphamide, cisplatin, oxaliplatin, and irinotecan. These include diarrhoea, stomatitis, alopecia, bladder, kidney, and bone marrow toxicities. Protection from lethal toxicity by MSC was associated with enhanced antitumour activity in rats bearing advanced Ward colorectal carcinoma and in nude mice bearing human squamous cell carcinoma of the head and neck, FaDu, and A253 xenografts.

Conclusions:

Se-methylselenocysteine offers selective protection against organ-specific toxicity induced by clinically active agents and enhances further antitumour activity, resulting in improved therapeutic index. These data provided the rationale for the need to clinically evaluate MSC as selective modulator of the antitumour activity and selectivity of anticancer drugs.     

Preclinical evaluation of the anticancer activity and toxicity of 9-nitro-20(S)-camptothecin (Rubitecan).

The purpose of this study is to establish the maximum tolerated dose of rubitecan in mice, dogs and men and to establish the anticancer activity of such dose against human tumors xenografted in nude mice. Nude mice received increasing doses of Rubitecan by intrastomach injection until the maximum tolerated dose (MTD) had been established for both the single dose and the multiple doses at the schedule of 5 days on, 2 days off. Extrapolating from the mouse data, MTD was determined for oral administration in dogs and man. Levels of the drug in plasma were determined by high pressure liquid chromatography (HPLC). Using maximum tolerated multiple doses, the sensitivity of human cancer xenografts in nude mice to Rubitecan was determined. MTD of Rubitecan in mice for multiple doses intrastomach at the schedule of 5+,2- was 1 mg/kg/day. MTD in dogs was also 1 mg/kg/day, administered orally but at the schedule of 4+,3-. In man, it was 1 mg/m2/day at the schedule of 5+,2-. Treatment of human cancer xenografts in nude mice with MTD of Rubitecan resulted in 100% growth inhibition of 30/30 tumors tested and in 24/30 in their total disappearance. These 30 tumors comprised all the most common human cancers: lung, colorectal, breast, pancreatic, ovarian, prostate, stomach, melanoma and a leukemia. From the data collected, it appears that rubitecan is a very promising anticancer drug with high potency against a wide spectrum of human cancers. These cancers growing as xenografts in nude mice are always growth inhibited (30/30) and frequently (24/30) totally destroyed by the administration of non-toxic doses of Rubitecan.     

GEM 231, a second-generation antisense agent complementary to protein kinase A RIalpha subunit,potentiates antitumor activity of irinotecan in human colon,pancreas, prostate and lung cancer xenografts

GEM 231, a second-generation antisense oligonucleotide targeted against the RIalpha subunit of protein kinase A (PKA) was co-administered with the chemotherapeutic agent irinotecan, a topoisomerase-I inhibitor, to study the antitumor efficacy of the combination in nude mice bearing various human tumor xenografts. The combination treatment of GEM 231 and irinotecan produced enhanced and prolonged tumor-growth inhibition, compared with irinotecan monotherapy, against human colon (HCT-116), pancreas (Panc-1), prostate (PC3) and lung (SKMES) tumors in mice. The extent of tumor-growth inhibition, however, varied among the different tumor models studied. The tumor-growth inhibition depended on the dose of GEM 231 co-administered with irinotecan. The combination of GEM 231 (20 mg/kg, i.p., 5 days on 2 days off x 7) and irinotecan (50 mg/kg, i.v., qwk x 3) produced significantly longer tumor-growth delay than did irinotecan administered alone. Importantly, the co-administration of irinotecan and GEM 231 did not result in higher toxicity compared with monotherapies in the several tumor models tested. These results suggest that the use of irinotecan in combination with GEM 231 may increase the therapeutic index of irinotecan in cancer patients.     

Selenium protects against toxicity induced by anticancer drugs and augments antitumor activity: a highly selective, new, and novel approach for the treatment of solid tumors

Limited therapeutic selectivity and tumor resistance are major obstacles to current chemotherapy. The development of new therapeutic modalities for solid tumor remains a challenge. The use of selenium, 5-methylselenocysteine (MSC), or seleno-L-methionine (SLM) as selective modulators of anticancer drugs is novel and has not been previously investigated. Selenium deficiency is associated with an increased risk of cancer and cancer death. Although low-dose selenium supplementation has been investigated in a large randomized prevention trial, its potential in chemotherapy toxicity prevention and enhancement of antitumor activity of anticancer drugs has not been evaluated. An ideal biomodulator of anticancer drugs would allow escalation of drug dose with the hope of enhancing antitumor activity and possibly reversing drug resistance. Results from this laboratory have demonstrated that MSC and SLM are highly effective modulators of irinotecan cure rates in de novo sensitive and resistant human tumor xenografts. Studies in mice have documented that the minimum effective dose of MSC when combined with irinotecan is 0.01 mg daily. The optimal schedule is to administer MSC orally for 7 days before and concurrently with irinotecan. The observed effects were not drug-specific, as similar results were obtained with taxanes, platinum agents, 5-fluorouracil, and anthracyclines; nor were they species-specific, as selective effects were obtained in mice and rats and are currently being confirmed in ongoing clinical trials.     

Overexpression of Bax enhances antitumor activity of chemotherapeutic agents in human head and neck squamous cell carcinoma.

Overexpression of the Bax protein in human head and neck squamous cell carcinoma A253 cells was reported to result in an increased sensitivity to various chemotherapeutic agents in vitro (Guo et al., Oncol. Res., 11: 91-99, 1999). In the present study, the relationship between Bax expression and response to chemotherapy was further investigated in vitro and in vivo model systems. For in vitro study, A253, A253/Vec (pcDNA3 vector transfectant), and A253/Bax (pcDNA3/Bax transfectant, expressing 50-fold higher Bax protein than A253 and A253/Vec) cells were exposed to various concentrations of raltitrexed (a specific thymidylate synthase inhibitor) and SN-38 (a topoisomerase I inhibitor) for 2 h, and cell growth inhibition was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide clonogenic assay. Compared to A253/Vec, A253/Bax cells exhibited 9.5- and 13.5-fold increases in sensitivity to raltitrexed and SN-38, respectively. For in vivo study, A253/Vec and A253/Bax tumor xenografts were established by s.c. injection of tumor cells into nude mice. The antitumor activity and toxicity of raltitrexed (i.v. push daily for 5 days) and irinotecan (a prodrug of SN-38; i.v. push daily for 3 days) were evaluated. The maximum tolerated doses of raltitrexed and irinotecan were 30 and 100 mg/kg/day, respectively. At the maximum tolerated doses, minimal antitumor activity was observed with raltitrexed, although irinotecan was more active than raltitrexed against A253 or A253/Vec tumors. In contrast, both raltitrexed and irinotecan were significantly more active against A253/Bax xenografts than against A253/Vec xenografts; the yield for complete tumor regression (cure) was 40% and 100% with raltitrexed and irinotecan, respectively, with no significant toxicity. Furthermore, the observed increase of antitumor activity in A253/Bax tumors was associated with an enhanced induction of apoptosis in vivo. The in vivo results demonstrated a proof of the principal concept that selecting up-regulation of the proapoptosis gene Bax can provide the basis for a greater therapeutic efficacy to a variety of chemotherapeutic agents with different structures and mechanisms of action.     

Activity of the Vascular-Disrupting Agent 5,6-Dimethylxanthenone-4-Acetic Acid against Human Head and Neck Carcinoma Xenografts

Head and neck squamous cell carcinomas (HNSCC) constitute a majority of the tumors of the upper aerodigestive tract and continue to present a significant therapeutic challenge. To explore the potential of vascular-targeted therapy in HNSCC, we investigated the antivascular, antitumor activity of the potent vascular-disrupting agent (VDA) 5,6-dimethylxanthenone-4-acetic acid (DMXAA) against two HNSCC xenografts with markedly different morphologic and vascular characteristics. Athymic nude mice bearing subcutaneous FaDu (human pharyngeal squamous cell carcinoma) and A253 (human submaxillary gland epidermoid carcinoma) tumors were administered a single dose of DMXAA (30 mg/kg, i.p). Changes in vascular function were evaluated 24 hours after treatment using contrast-enhanced magnetic resonance imaging (MRI) and immunohistochemistry (CD31). Signal enhancement (E) and change in longitudinal relaxation rates (ΔR₁) were calculated to measure alterations in vascular perfusion. MRI showed a 78% and 49% reduction in vascular perfusion in FaDu and A253 xenografts, respectively. CD31-immunostaining of tumor sections revealed three-fold (FaDu) and two-fold (A253) reductions in microvessel density (MVD) 24 hours after treatment. DMXAA was equally effective against both xenografts, with significant tumor growth inhibition observed 30 days after treatment. These results indicate that DMXAA may be beneficial in the management of HNSCC, alone or in combination with other treatments.     

Variable sensitivity of endothelial cells to epirubicin in xenografts of human nasopharyngeal carcinoma CNE-2 cells

Conventional anticancer drugs show non-specific vascular toxicity, and using anticancer drugs as angiogenesis inhibitors was suggested. However, our previous study suggested that vascular endothelial growth factor (VEGF) protected endothelial cells against chemotherapy drugs in vitro. To further test whether the vascular toxicity of anticancer drugs is active in vivo, epirubicin was i.p. injected into nude mice with s.c. xenografts of human nasopharyngeal carcinoma CNE-2 once (one-day schedule) or once a day from day 1 to day 7 (seven-day schedule). At 48 hours after the single injection or the 7th injection tumors were removed for detection of apoptosis of vascular endothelial cells vessels and the content of VEGF in tumor tissues. The results showed that epirubicin damaged tumor microvessels when the drug was given as a single dose, whereas epirubicin lost its vascular toxicity when the drug was given continuously for seven days, accompanied by higher levels of VEGF in tumor tissues. These results suggest the sensitivity of endothelial cells lining tumor vessels is variable during chemotherapy, and the protective effect of VEGF on endothelial cells might be related to the schedule of administration.     

Interaction of interleukin-11 (rhIL-11) with cytotoxic therapies in the human HT-29 colon carcinoma

The cytokine interleukin-11 (rhIL-11) has been shown to enhance the recovery of bone marrow, oral epithelium and intestinal crypt cells after cytotoxic insult by anticancer drugs or ionizing radiation. 5-Fluorouracil based chemotherapy and radiation therapy are frequently used in the treatment of colon cancer. Simultaneous exposure of human HT-29 colon carcinoma cells in culture to rhIL-11 and 5-fluorouracil for 24 h resulted in enhanced cell killing of the HT-29 cells with lower concentrations (1-10 mu M) of 5-fluorouracil compared with the drug alone. Exposure of HT-29 cells to rhIL-11 prior to, during and after radiation delivery did not alter the killing of normally oxygenated or hypoxic HT-29 cells by the radiation. In vivo treatment of nude mice bearing HT-29 colon tumor xenografts with rhIL-11 prior to and during administration of 5-fluorouracil did not alter the killing of the tumor cells or the killing of the bone marrow CFU-GM by the drug. In the tumor growth delay experiments, administration of rhIL-11 to nude mice bearing HT-29 colon tumor xenografts did not alter the growth of the tumor and did not alter the response of the tumor to 5-fluorouracil. However, administration of rhIL-11 to these animals increased the response of the tumor to fractionated radiation therapy resulting in a radiation dose-modifying factor of 1.5+/-0.2. These results indicate that rhIL-11 may be a selective protector of normal tissues without affecting the response of the tumor to therapy.     

Lack of microvessels in well-differentiated regions of human head and neck squamous cell carcinoma A253 associated with functional magnetic resonance imaging detectable hypoxia, limited drug delivery, and resistance to irinotecan therapy.

PURPOSE: Combination chemotherapy with irinotecan (CPT-11; 50 mg/kg/week x 4 intravenously), followed 24 hour later by 5-fluorouracil (50 mg/kg/week x 4 intravenously), results in 10 and 100% cure rates of animals bearing human head and neck squamous cell carcinoma xenografts A253 and FaDu, respectively. A253 consists of 30% well-differentiated and avascular and 70% poorly differentiated regions with low microvessel density (10/x400), whereas FaDu is uniformly poorly differentiated with higher microvessel density (19/x400). Studies were carried out for determining the role of well-differentiated and avascular regions in drug resistance in A253 and detection of such regions with noninvasive functional magnetic resonance (fMR) imaging. EXPERIMENTAL DESIGN: Tumors were harvested for histopathologic evaluation and immunohistochemistry (CD31, CD34; differentiation marker: involucrin; hypoxia markers: carbonic anhydrase IX, pimonidazole; vascular endothelial factor (VEGF) and Ki67) immediately after fMR imaging following the 3rd dose of chemotherapy. High-performance liquid chromatography determination of intratumoral drug concentration of 7-ethyl-10-hydroxyl-camptothecin and autoradiography with (14)C-labeled CPT-11 was done 2 hours after CPT-11 administration. RESULTS: Although A253 xenografts showed three times higher concentration of 7-ethyl-10-hydroxyl-camptothecin, FaDu was more responsive to therapy. After therapy, A253 tumor consisted mostly (approximately 80%) of well-differentiated regions (positive for involucrin) lacking microvessels with a hypoxic rim (positive for carbonic anhydrase IX and pimonidazole) containing few proliferating (Ki67 positive) poorly differentiated cells. Autoradiography revealed that well-differentiated A253 tumor regions showed 5-fold lower (14)C-labeled CPT-11 concentrations compared with poorly differentiated areas (P < 0.001). Blood oxygen level dependant fMR imaging was able to noninvasively distinguish the hypoxic and well-vascularized regions within the tumors. CONCLUSION: Avascular-differentiated regions in squamous cell carcinoma offer sanctuary to some hypoxic but viable tumor cells (carbonic anhydrase IX and Ki67 positive) that escape therapy because of limited drug delivery. This study provides direct evidence that because of a specific histologic structure, avascular, well-differentiated hypoxic regions in tumors exhibit low drug uptake and represent a unique form of drug resistance.     

单克隆抗体CH12抑制头颈部鳞状细胞癌裸鼠种植瘤的生长

目的:观察嵌合型单克隆抗体CH12对头颈部鳞状细胞癌(head and neck squamous cell carcinomas,HNSCC)裸鼠种植瘤生长的抑制作用,为进一步研究CH12单抗在肿瘤治疗中的作用提供参考数据。方法:Western blotting检测5种HNSCC细胞系A253、CAL27、Detroit 562、FaDu和RPMI 2650中表皮生长因子受体(epidermal growth factor receptor,EGFR)的表达,流式细胞术检测CH12单抗同这5种细胞系的结合能力。皮下接种CAL27和A253细胞,建立HNSCC裸鼠种植瘤模型。模型鼠腹腔注射CH12单抗,以PBS作为阴性对照,观察肿瘤生长情况,绘制肿瘤生长曲线。结果:EGFR在CAL27、A253、FaDu及Detroit 562细胞中均有不同程度的表达,其中CAL27细胞中EGFR的表达水平最高,A253细胞次之。CH12单抗与5种HNSCC细胞系的结合能力由高到低依次为CAL27、FaDu、A253、Detroit 562和RPMI 265细胞。CH12单抗对CAL27和A253细胞裸鼠种植瘤的生长均有显著抑制作用,抑瘤率分别为56.8%(P=0.022)和59.7%(P=0.015)。结论:单克隆抗体CH12对EGFR高表达的HNSCC细胞种植瘤的生长具有明显的抑制作用。     

Pharmacokinetic profile of the microtubule stabilizer patupilone in tumor-bearing rodents and comparison of anti-cancer activity with other MTS in vitro and in vivo

Introduction  Patupilone is a microtubule stabilizer (MTS) currently in clinical development. Here, we evaluate the anti-cancer activity in vitro and in vivo in comparison to paclitaxel and describe the pharmacokinetics (PK) of patupilone in tumor-bearing nude mice and rats. Methods  The potency in vitro of patupilone and two other MTS, paclitaxel and ixabepilone, was determined using human colon carcinoma cell lines with low (HCT-116, HT-29, RKO) and high (HCT-15) P-glycoprotein expression (P-gp), as well as two multi-drug resistance (MDR) model cell pairs, MCF7/ADR and KB-8511 cells and their respective drug-sensitive parental counterparts. The PK of patupilone was investigated in nude mice bearing HCT-15 or HT-29 xenografts and in rats bearing s.c. pancreatic CA20498 tumors or A15 glioma tumors. Anti-cancer activity in vivo was compared to that of paclitaxel using three different human tumor colon models. The retention and efficacy of patupilone was compared in small and large HT-29 xenografts whose vascularity was determined by non-invasive magnetic resonance imaging. Results  Patupilone was highly potent in vitro against four different colon carcinoma cell lines including those showing multi-drug-resistance. In contrast, paclitaxel and ixabepilone displayed significantly reduced activity with markedly increased resistance factors. In both rats and mice, a single i.v. bolus injection of patupilone (1.5–4 mg/kg) rapidly distributed from plasma to all tissues and was slowly eliminated from muscle, liver and small intestine, but showed longer retention in tumor and brain with no apparent elimination over 24 h. Patupilone showed significant activity against three human colon tumor models in vivo, unlike paclitaxel, which only had activity against low P-gp expressing tumors. In HT-29 tumors, patupilone activity and retention were independent of tumor size, blood volume and flow. Conclusions  The high potency of patupilone, which is not affected by P-gp expression either in vitro or in vivo, and favorable PK, independent of tumor vascularity, suggest that it should show significant activity in colorectal cancer and in other indications where high P-gp expression may compromise taxane activity.     

Antisense oligonucleotide targeted to RIalpha subunit of cAMP-dependent protein kinase (GEM231) enhances therapeutic effectiveness of cancer chemotherapeutic agent irinotecan in nude mice bearing human cancer xenografts: in vivo synergistic activity,pharmacokinetics and host toxicity

The RIalpha-subunit of cAMP-dependent protein kinase (PKA) is overexpressed in various human cancers and PKA has been suggested to be a potential target for cancer therapy. We have shown an antisense oligonucleotide with advanced chemistry (mixed-backbone oligonucleotide) targeted to PKA RIalpha-subunit (GEM231) to have anti-tumor activity in vitro and in vivo. In the present study, we demonstrated synergistic effects between the anti-PKA antisense oligonucleotide and the clinically used anticancer agent irinotecan, using nude mouse models of human cancers of colon (LS174T and DLD-1), breast (MCF-7), prostate (DU-145 and PC-3) and lung (H1299). To elucidate the underlying mechanisms, in vivo pharmacokinetics of irinotecan was determined following pre-treatment of oligo GEM 231 in CD-1 mice and nude mice bearing LS174T xenografts. GEM 231 increased tissue uptake of irinotecan. However, no significant change in host toxicity was observed following combination treatment of irinotecan and GEM231 compared with irinotecan alone. These results suggest that GEM231 have a role in irinotecan metabolism and its antitumor activity, providing a basis for future development of this oligonucleotide as a chemosensitizer for irinotecan-based therapy.     

Radiation response of xenografts of a human squamous cell carcinoma and a glioblastoma multiforme: a progress report

Human cell lines derived from squamous cell carcinomas of the pharynx (FaDu and HSCC6) and glioblastoma multiforme (U87, A2, A7, MMC-1, MMC-2) have been studied in vitro as monolayers in exponential (all 7 cell lines) or plateau phase (FaDu and U87), and as 1 mm diameter spheroids in vitro (FaDu and U87) and as 6 mm diameter xenografts growing in the legs of athymic NCr(nu/nu) nude mice (FaDu, HSCC6, U87, A7 cells). For SF2s and D values, there was broad overlap of values between SCC and glioma cell lines. In contrast, the D0 values were higher for U87, A2, A7, and MCC-1 than the two SCC cell lines, while the extrapolation numbers were greater for the two SCC lines than any of the glial tumor lines (these differences were not regularly significant). Complete dose response assays for local control of FaDu, HSCC6, U87, and A7 xenografts have been performed under conditions of normal blood flow and clamp hypoxia for tumors growing in mice which had received 6 Gy WBI at 24 hr before transplantation. Under the latter circumstances, irradiations have been performed on FaDu and U87 as single doses or as 2, 4, or 8 equal doses; for the fractionated irradiation, treatments were given on a BID basis with 4 hr between the treatments on any 1 day. For irradiation of 1 mm diameter spheroids, radiation was administered as single doses under conditions of equilibration with AIR. The TCD50 for the FaDu was significantly higher and the dose response curve steeper for tumors growing in immune suppressed (6 Gy WBI 24 hr prior to transplantation) than in control nude mice. Tumors, exponential or plateau phase cells, and spheroids derived from U87 were significantly and substantially more resistant under all conditions and fractionation schedules than for FaDu. Thus, the in vitro results do not indicate a clearly greater resistance by the glioma cell lines, while the more limited TCD50 data (single dose and 8 fractions irradiation) show more resistance in vivo by the glial tumors. We noted that the TCD50 values for U87 and A7 glial tumors overlap those for spontaneous tumors of the C3H mouse but are higher than the human squamous cell carcinoma xenografts in the nude mice. Substantial additional data from xenografts are needed to determine if the higher TCD50 values for GBMs, especially for fractionated irradiation, is a regular finding and is of sufficient magnitude to be pursued by studies to explain the observed differences.     

Complete regression of xenografted human carcinomas by camptothecin analogue-carboxymethyl dextran conjugate (T-0128)

Clinically available camptothecins (CPTs), such as irinotecan (CPT-11) and topotecan, represent one of the most promising classes of antitumor agents, despite their toxicity. To improve their pharmacological profiles, a new macromolecular prodrug, denoted T-0128, was synthesized. This prodrug is a novel CPT analogue (T-2513)-carboxymethyl (CM) dextran conjugate via a triglycine spacer, with a molecular weight of Mr 130,000. This study was designed to test the concept that the rational design of a CPT-polymer conjugate would increase the efficacy of the parent drug. The in vivo antitumor study against Walker-256 carcinoma demonstrated that T-0128 was 10 times as active as T-2513, supporting this concept. Additionally, comparative efficacy studies of T-0128, T-2513, CPT-11, and topotecan were performed using a panel of human tumor xenografts in nude mice, showing the advantage of T-0128 over these CPTs. The maximal tolerated doses (MTDs) of T-0128, T-2513, and CPT-11 were comparable. Even a single i.v. injection of T-0128 at 6 mg/kg (based on the amount of T-2513 bound to CM dextran) induced complete regression of MX-1 mammary carcinoma. T-0128 at 10 mg/kg weekly for 3 weeks (one-tenth of its MTD) cured LX-1 lung carcinoma. Also, T-0128 below its MTD consistently cured or regressed St-4 gastric and HT-29 colorectal tumor xenografts that are highly refractory to CPTs. These demonstrate the broad range of therapeutic doses achieved with T-0128. Pharmacokinetic studies were performed to correlate the efficacy results obtained for T-0128 with plasma and tissue drug concentrations using Walker-256 tumor-bearing rats. Results showed that after i.v. administration of T-0128, the conjugate continued to circulate at a high concentration for an extended period, resulting in tumor accumulation. In the tumor, the sustained release of T-2513 occurred. In contrast, T-2513 disappeared rapidly from the body. The significant increases in the amount and exposure time of released T-2513 in the tumor explain well the enhanced efficacy of T-0128. In conclusion, this study indicated that T-0128 improved the potency of T-2513, demonstrating the proof of the above concept.     

Antitumour activity of XR5944 in vitro and in vivo in combination with 5-fluorouracil and irinotecan in colon cancer cell lines

XR5944 (MLN944), a novel bis-phenazine, has demonstrated potent cytotoxic activity against a variety of murine and human tumour models. In the present study, the antitumour activity of XR5944 was investigated in combination with 5-fluorouracil (5-FU) or irinotecan in human colon carcinoma cell lines and xenografts. In vitro cytotoxicity of the combinations following exposure to the drugs sequentially or simultaneously was evaluated by the sulphorhodamine-B assay and interactions were determined using median-effect analysis. Antagonism was observed (CI >1) following exposure of HT29 cells simultaneously to XR5944 and 5-FU or SN38 (active metabolite of irinotecan). In contrast, sequential exposure of either combination in either order demonstrated at least an additive response (CI< or =1). At least an additive response was also observed with these combinations in HCT116 cells regardless of schedule. Antitumour activity in HT29 xenografts in nude mice was enhanced by sequential administration of 5-FU (65 mg kg(-1)) or irinotecan (CPT-11) (35 mg kg(-1)) 48 h before XR5944 (5, 10, or 15 mg kg(-1)) compared to single agent treatment at the same or higher doses. Administration of irinotecan (35 mg kg(-1)) and XR5944 (15 mg kg(-1)) just 30 min apart yielded similar efficacy to sequential administration 48 h apart. All combinations were well tolerated. These data suggest that combinations of XR5944 with irinotecan or 5-FU are of significant interest in the treatment of colon cancer.     

A phase I and pharmacokinetic study of fixed-dose selenomethionine and irinotecan in solid tumors.

PURPOSE: We conducted a phase I study to determine the maximum tolerated dose (MTD) of irinotecan with fixed, nontoxic high dose of selenomethionine. EXPERIMENTAL DESIGN: Selenomethionine was given orally as a single daily dose containing 2,200 mug of elemental selenium (Se) starting 1 week before the first dose of irinotecan. Irinotecan was given i.v. once weekly x 4 every 6 weeks (one cycle). The starting dose of irinotecan was 125 mg/m(2)/wk. Escalation occurred in cohorts of three patients until the MTD was defined. Pharmacokinetic studies were done for selenium and irinotecan and its metabolites. RESULTS: Three of four evaluable patients at dose level 2 of irinotecan (160 mg/m(2)/wk) had a dose-limiting diarrhea. None of the six evaluable patients at dose level 1 (125 mg/m(2)/wk irinotecan) had a dose-limiting toxicity. One patient with history of irinotecan-refractory colon cancer achieved a partial response. The long half-life of selenium resulted in a prolonged accumulation towards steady-state concentrations. No significant changes in the pharmacokinetics of CPT-11, SN-38, or SN-38G were identified; however, the coadministration of selenomethionine significantly reduced the irinotecan biliary index, which has been associated with gastrointestinal toxicity. CONCLUSIONS: Selenomethionine at 2,200 mug/d did not allow the safe escalation of irinotecan beyond the previously defined MTD of 125 mg/m(2). None of the patients receiving 125 mg/m(2) of irinotecan had grade >2 diarrhea. Unexpected responses and disease stabilizations were noted in a highly refractory population. Further escalation of selenomethionine is recommended in future trials to achieve defined protective serum concentrations of selenium.     

In vivo antitumor activity of choline kinase inhibitors: a novel target for anticancer drug discovery.

Transformation by some oncogenes is associated with increased activity of choline kinase (ChoK), resulting in elevated constitutive levels of phosphorylcholine, a proposed second messenger required for DNA synthesis induced by growth factors. Here we describe the characterization of ChoK inhibitors with antiproliferative properties against human tumor-derived cell lines. The new molecules were tolerated in mice at doses that showed in vivo antitumor activity against human tumor xenografts derived from HT-29 and A431 cell lines implanted s.c. in nude mice. This first generation of inhibitors provides in vivo evidence that blockade of phosphorylcholine production is a valid strategy for the development of new anticancer agents, opening a new avenue for the development of antitumor drugs with a novel mechanism of action.